Dampening device and method for lithographic offset printing plate



Feb. 28, 1961 H. P. DAHLGREN DAMPENING DEV Filed April 9, 1956 2Sheets-Sheet 1 INVENTOR m M H Li.

ATTORNEYS Feb. 28, 1961 H. P. DAHLGREN 2,972,944

DAMPENING DEVICE AND METHOD FOR LITHOGRAPHIC OFFSET PRINTING PLATE 2Sheets-Sheet 2 Filed April 9. 1956 INVENTOR Hero/d A? Dab/grew D 0 0 3BY k m ATTORNEY s DAMPENING DEVICE AND METHOD FOR LITHO- GRAPHIC OFFSETPRINTING PLATE Harold P. Dahlgren, Mobile, Ala. (6919 Blackwood, Dallas31, Tex.)

Filed Apr. 9', 1956, Ser. No. 577,031

11 Claims. c1. 101 -148 This invention is concerned with an improvementin dampening devices for lithographic offset printing plates and it isparticularly concerned with a dampening device wherein water or otherliquid is atomized and propelled against, and deposited on, an inkapplying form roller or other intermediate roller from whence it isdeposited on the plate.

A lithographic offset printing plate is chemically treated so that theprinting or image area thereon has an afinity for the relatively greasyink and the non-printing area thereon has an afiinity for moisture. Itis necessary to apply moisture to the non-printing area of the plate inorder to keep it from receiving ink.

Various means have been employed in the past for applying moisture tothe printing plate, none of which have been entirely satisfactory.

Such means of applying moisture to the plate have included wicks orswabs which wiped against the plate as it rotates, individual sprayheads spaced along the length of the plate drum, air jets which blewmoisture from a fabric belt or screen, the mixing of water with the inksupply and applying it directly to the inking rollers, and theapplication of moisture to the plate by means of fabric covered rollerswhich dip into awater pan and roll directly against the plate to depositmoisture thereon. The latter means is the most common type of dampeningdevice presently employed.

All of these plate moistening systems have proven deficient for onereason or another. Use of swabs or wicks bearing directly against theplate damage the plate by friction, thus decreasing the life of theplate, and they do not provide uniform distribution of moisture. The useof spray heads is unsatisfactory because of the difiiculty of adjustingthe spray heads to apply the correct amount of moisture, and theyusually supply more moisture than is needed or is desirable.

The use of air jets to blow moisture onto the plate also presents theproblem of proper adjustment to supply the desired amount of moisture tothe plate.

Furthermore the use of spray heads and air jets presents the problem ofproper lateral distribution of moisture to the plate, in that moremoisture would be applied at some points than others.

The mixing of water with the ink supply causes the ink to emulsify. Theemulsified fluid becomes unevenly distributed on the ink rollers,resulting in poor quality of the printed material.

Another means of applying moisture to the printing plate was thecondensation of steam on the plate. Such means was found deficientbecause the plate became heated by the steam to such an extent as toprevent condensation. It was attempted to solve this problem by coolingthe plate cylinder by artificial means as the steam was applied, butthis required complicated and clumsy mechanisms which were difficult toadjust to apply the proper amount of moisture to the plate and tomaintain even distribution thereof.

' 2,972,944 7 atented Feb. 2%, 1961 directly to the offset printingplate, which is the dampening means most universally employed at thistime, has proven inadequate because the fabric soon becomes impregnatedand encrusted with ink by direct contact with the plate, resulting in.the necessity for repeated changing of the rollers, which results incostly down time of the press and unnecessary labor. It is also alaborious task to change the fabric on the rollers.

Excess water accumulates in the fabric covered dampener rolls whichoften necessitates the stopping of 'thepress to allow the rolls to dry.

Furthermore, when the press is started sufiicient time must be allowedto cause'the. rolls to be evenly saturated with water, thus resulting inlost production.

After a time the fabric covered dampener rolls become worn by frictionalcontact with the plate causing lint from the fabric to be deposited onthe printing area of the plate. The water saturated lint causes whitespecks on the printed matter.

The frictional contact of the dampener rollers causes deterioration andwear on the plate, resulting'in distortion and loss of printed images.

When ink color is changed dampener covers. must usually be changed, sothat impregnated pigment from prior color does notcontaminate new color.

By reason of the change in the absorptive character dampening devicewhich is not in physical contact with the plate and in one withnon-changing mechanical aspects'. This would assure consistency anduniformity of moisture supply and distribution. This invention isintended to solve that problem.

In my co-pending application for patent, Serial No. 458,226, filedSeptember 24, 1954, now Patent No. 2,868,-

' 118, issued J anuary' 13, 1959, therewas disclosed a dampening' devicewherein atomized moisture was applied directlyito the face of thelithographic offset printing plate bymeans of a rotary brush whichflicked water from the surface of a rotary waterconveyor roller as thebrush and roller rotated in contact. i V 1 The advantages of thissystem, as set forth in said copending application, are that moisture isconveyed to the plate without physical contact therewith; it is evenlydistributed laterally across the face of the plate as it rotates; thereis no wear or abrasion to the plate by friction; and it is possible toaccurately adjust the amount of moisture applied to the plate byadjusting the speed of rotation of the water'conveyor roller. By usingsuch system it is possible to accurately adjust the amount of moistureto be applied to the plate for each job, and it is unnecessary toreadjust same during the operation of the press. No foreign matter, suchas lint, is deposited on the plate.

The moisture applying brush is durable' an'd long lasting,

thus resulting in a great savings in labor and down time of the press.

Although the system of applying moisture directly to the plate "by suchbrush, as disclosed in' said co-pending application, has the advantagehereinbefore stated and would have particular use in a web-fed ofisetpress, wherein there is no gap in the plate cylinder, it has been foundthat in applying moisture directly to the plate in a lithographic ofisetpress, wherein there is'a gap in the cylinder for attaching the ends ofthe plate, it is desirable to apply the moisture to the plate indirectlyby depositing it on one of the inking form rollers from whence it isdeposited on the plate. of moisture in the gap which would, in someinstances, .cause the accumulation of excessive moisture on the plate atthe edges of the gap. a

In said co-pending application a cam arrangement was provided forlifting the brush away from the water conveyor roller as the brushpassed the gap in order to pre- .vent deposit of moisture in the gap.The improvement, forming the basis of this application, eliminates thenecessity of such cam arrangement and also prevents the deposit ofmoisture in the gap.

The present invention includes the basic advantages of the employment ofthe said brush to atomize, propel, distributeand deposit moisture on theplate and at the same time offers an improvement which makes ituniversally applicable to all types of lithographic offset printingwherein moisture must be applied to the plate, and at the same timesimplifies the system and provides for more even distribution ofmoisture on the non-image area of the plate.

It is therefore a primary object of this invention to provide means forapplying moisture to lithographic offset printing plates wherein themoisture may be applied in regulated quantities, and evenly anduniformly distributed on the plate without repeated adjustment.

Another object is to provide a dampening means for lithographic offsetprinting plates wherein lateral distribution of the moisture is attainedand maintained without repeated adjustment.

A still further object is to provide dampening means for lithographicoffset printing plates which is durable and long-lived and results inthe reduction to a minimum of down time of the press. i

Still another object is to provide a dampening device for a lithographicofiset printing plate which is simple to operate and relativelyinexpensive-to manufacture, and is easy to adjust, install and remove.

A further object is to provide av dampening means for lithographicoffset printing plates wherein moisture is applied uniformly and evenlyto an inking form roll or other intermediate roller in rotative contactwiththe plate from whence it is deposited on the plate, thus preventingmoisture from collecting in the plate cylinder p Another object of thisinvention is to provide a dampening device for lithographic oflsetprinting plates which employs a brush rotated against a wet surface toflick moisture off the surface in atomizedparticles and projects orpropels the atomized particles in a controlled stream of moistureagainst the face-of an inking form roller or other roller from whence itis deposited on the face of the plate as the roller rolls thereagainst.

Other and further objects of my invention will become apparent uponreading the ensuing specification and by referring to the drawingsannexed hereto.

. A suitable embodiment of my invention is shown in the attacheddrawings,-in which;

Fig. I is a fragmentary cross-sectional elevational view of alithographic offset printing press having attached thereto the platedampening mechanism comprising the improvements with which thisinvention is concerned. In said view the plate dampening mechanism isshown in operative position, wherein moisture is being applied Thiseliminates the accumulation 1 to the surface of a form roller which isin rotative contact with the plate cylinder. In said view only suchportions of the lithographic offset press are shown, as will show theconnection of said dampening device to said the offset press, whichpermits the retraction of the tion of the said improved dampeningdevice.

Fig. II is a view similar to Fig. I, showing the dampening device inretracted position, with the form rollers disengaged from the platecylinder and the rotatable brush disengaged from the liquid conveyingroll.

Fig. III is a fragmentary cross-sectional view taken on the line IIIIIIof Fig. I, showing the slidable mounting of the dampening device frameon the end frame of the offset press, which permits the retraction ofthe dampening device frame when the press is shifted to nonimpressionposition.

Fig. IV is a fragmentary plan view of the water conveyor roller showingthe knurled or roughened surface of the roller. p Numeral references areemployed to designate the various parts of the devices shown in thedrawings, and like numerals indicate like parts throughout the variousfigures of the drawings.

The numeral 1 indicates a fragmentary portion of one of the side framesof a conventional lithographic offset printing press. It is believedunnecessary for the purpose of the disclosure of this invention toillustrate a complete lithographic offset printing press, theconstruction and operation of which are Well-known to those skilled inthe art. This invention is specifically addressed to a dampening devicefor applying moisture to the plate, and only such portions of the pressare shown as will illustrate, and provide a proper orientation, for theconstruction and operation of therdampening device.

It will be understood that there is a side frame l at each side of thelithographic offset press, and that the view shown in Figs. I and IIhereof are elevational sectional views taken at a point intermediate thesides of the press and looking toward one of the sides.

The plate cylinder 2 is mounted on a shaft 3, which shaft is journaledat each end to the side frames 1. A lithographic offset plate 4 isarranged about, and secured to, the outer side of the plate cylinder 2by means of clamp elements 6, whiehare recessed in the gap 5 in theperiphery of the plate cylinder 2, and in a manner which is well-knownin the art.

A blanket cylinder 7, which has on its outer surface a covering ofspecially treated and prepared rubber material,.is'mounted on a shaft 8which is journaled at each end to the end frames 1.

.The impression cylinder 9 is mounted on a shaft 10 which is alsojournaledat its opposite ends to the end frames 1.

Gears 11, 12 and 13 are secured to the shafts 3, 8 and 10, respectively,at the ends thereof, whereby the cylinders 2, 7 and 9 are rotated inunison from a suitable power source (not shown).

An inking vibrator roller 14, which is usually of metallic construction,is mounted on a shaft 15 which is journaled at each end to the endframes 1. Ink applying form roller 16, which is mounted on a shaft 17,journaled at each end to hanger arms such as shown at 30, is inrotatable contact with the vibrator roller 14, and with the printingplate 4.

Another form roller 18 is mounted on a shaft 19, which is journaled ateach end to hanger arms, such as shown at 30, and is in rotative contactwith the vibrator roller 14 and the plate 4. The form rollers areusually made of resilient material such as relatively soft rubber. Inkis applied to the vibrator roller 14, which is transferred to the formrollers 16 and 18, and in turn to the printing plate 4, as the said formrollers rotate by frictional contact with the plate. The vibrator roller14 is rotated through conventional drive means such as a sprocket orgear secured to shaft 15, in a-manner which is well-known in the art.There may be a plurality of sets of co-acting vibrator and form rollerslike'those shown at 14, 16 and 18.

Another set of co-acting vibrator and form rollers is shown at 20, 22and 24, respectively, the said vibrator and form rollers being rotatablymounted upon shafts 21, 24 and 25 respectively. The shaft 21 isjournaled at each end to the end frames 1 and the shafts 23 and 25 arejournaled between hanger arms, such as shown at 30'. The said vibratorroller 20 is also rotatable by suitable drive means, such as a sprocketor gear secured to the shaft 21 therefor, in a manner which iswell-known to those skilled in the art. The form rollers 22 and 24 arerotatable by frictional contact with the plate 4.

The vibrator rollers, form rollers, plate cylinder, blanket cylinder andimpression cylinder are shown merely for the purpose of orientation ofthe dampening device, constituting the subject matter of this invention.The detailed construction, mounting and operation of these conventionalelements are well understood by those familiar with the art, constituteno part of the present invention, and it is not thought necessary toillustrate and describe same in more detail.

As is well-known in the art, ink is applied to the image area of theplate 4 by the form rollers in rotative contact therewith. The printingimpression is applied from the image area of the plate 4 to the rubbersurface of the blanket cylinder 7, which image is in turn transferredfrom the rubber surface of the blanket cylinder 7 to the paper, whichpasses between the blanket cylinder and the impression cylinder 9.

The typical form roller hanger arm 36} is pivotally connected to theshaft 21 for the vibrator roller 20, as indicated at 31. The lower endof hanger arm 39 is rotatably connected to the shaft 25 for the formroller 24, as indicated at 32.

An adjustment screw 33 threadably extends through the outer end of thehanger arm 30, and is secured in adjusted position by means of a setscrew 34. The adjustment screw 33 has a head 35 thereon, and theadjustment screw is so adjusted that the head 35 is in slidable contactwith the cam shaft 39 when the press and dampening device are inimpression position, as shown in Fig. I.

An upwardly extending bracket 36 is secured to the end frame 1 and acompression spring 38 is attached between the bracket 36 and the upperend of the hanger arm 30. Said spring 38 normally urges the upper end ofthe arm 36 downwardly, and the form roller 24 into contact with theplate 4.

A cam shaft 39 is journaled at each end to the end frames 1. A cam lobe48 is secured on the cam shaft 39, and is arranged to contact the head35 on the adjustment screw 33, when the cam shaft is rotated in aclockwise direction.

The crank arm 43 is secured at its lower end to the cam shaft 39, and ispivotally attached at its upper end to a rod 44.

The rod 44 is actuated by a cam, crank or electrically driven mechanism,forming a part of a conventional offset press, and since such actuatingmechanism forms no part of this invention, it is not thought necessaryto il1ustrate same.

in any event, it will be seen that when the rod 44 is moved to the rightin Fig. I, the cam shaft 39 is rotated clockwise by rotation of thecrank arm 43, thus bringing the cam lobe 40 into contact with the head35, thereby raising the upper end of the hanger arm 30, and pivoting itin a counterclockwise direction about the shaft 21, thereby moving theform roller 24 away from the plate 4, as shown in Fig. II. Such motionof the rod 44 will also move the dampening device carriage away from theform roller 24 in the manner which will be hereinafter described.

It will be understood that each of the form rollers 16, 18, 22 and 24 ismoved away from the cylinder 2 by means of a hanger arm and camarrangement, such as illustrated and described immediately hereabove andthat the hanger arm 30 and co-acting cam'lobe 40 and head 35 areduplicated at each side of the presss. Such hanger arm and camarrangement is illustrated only in connection with one of the formrollers as being a typical means for moving the form rollers away fromthe plate cylinder when the press is in non-printing position. Sucharrangement is conventional on printing presses of this type, andconstitutes no part of this invention, per se.

When the rod 44 is moved to the left in Fig. I, and the head 35 isreleased from the cam lobe 40, the compression spring 38 will pivot thearm 30 in a clockwise direction and again bring the form roller 24 intoengagement with the plate 4.

The dampening device is mounted on a retractable carriage which includesseparate side mounting plate 46 at each side of the lithographic offsetprinting press. A rack gear 47 is mounted to the side frames 1 at eachside of the press by means of Allen screws 47a. A flange 48 is securedto the mounting plate 46 by means of cap screws 49, in position so thatthe flange 48 overlaps, in slidable contact with, the inner edge of therack gear 47. The rack gear 47 is also in slidable contact with themounting plate 46.

A shaft 52 extends through, and is journaled to, the mounting plate 46.A gear 53 is aflixed to the shaft 52, the teeth on said gear beingintermeshed with the teeth on the rack gear 47. A crank arm 54 issecured at its lower end to the shaft 52, and is pivotally attached at56 to the link 55. The link 55 is pivotally attached at its upper end tothe rod 44, as indicated at 45.

It will be seen that when the rod 44 is moved to the right in Fig. I,the link 55 also moves to the right, which movement causes the gear 53to move along the rack 47, carrying with it the side frames 46 for thedampening device, thereby moving the entire dampening device carriage tothe right and away from the form roller 24, in non-impression position,as shown in Fig. II. This operation takes place simultaneously when theform rollers are shifted away from the plate 4-, as the movements areinitiated through a common actuating rod 44.

A fluid containing pan 59 extends between the side plates 46 at eachside of the dampening device frame and is secured at each end to sideplates 46. A quantity of fluid 60, which may be water, or some othersuitable plate wetting fluid, is disposed in said pan, the level thereofbeing'sufficient to allow the fluid conveying roller 61 to be partiallysubmerged in said fluid.

The fluid conveying roller 61 is mounted on a shaft 63 which isjournaled at each end to the side frames 46 for the dampening device.

The peripheral surface of the roller 61 is'preferably knurled or hasasimilar irregular surface contour 62 for the purposes which will behereinafter mentioned. As-the roller 61 is rotated it passes through thewetting fluid 60 and the fluid adheres to the surface thereof and isthusconveyed on the surface of the roller out of the pan 59.

A rotatable brush 64 is mounted on a shaft 66, which is journaled ateach end to the pivotal arm 67 (of which there is one at each side ofthe dampener frame). The arms 67 are pivotally mounted on a shaft 68which is affixed at each end to the side plates 46.

The rotatable brush 64 has bristles 65 secured thereto which bristlesare preferably made of relatively stifl, springy material, such asnylon. However, it will be understood that such bristles could be madeof other springy material such as stifi hair, fibre or metal. It hasbeen found, however, that nylon or like synthetic material is moresuitable because of its relatively stifi but springy characteristics andthe fact that it is durable, long lasting and is impervious to water. Inany event the bristles 65 should be of material having the capability ofbeing bent and deformed and of instantly springing back to normalposition when released.

It will be noted that when the dampening device is in impressionposition as shown in Fig. I, the bristles 65 of the brush are pressedagainst the surface of the roller 61' so that the roller actually entersthe bristles and causes them to be bent into unrelaxed position at thecontact point.

As indicated by arrows the roller 61 and the brush 64 are preferablyrotated in opposite directions but the brush would function to propelmoisture against the form roller 24 even though brush 64 and theroller'fil were rotated in the same direction. It will be seen that asthe brush 64 is rotated against the surface of the roller 61 thebristles 65 are depressed against the surface of the roller as they passthereover, thus wiping the wetting fluid from the surface of the roller.As the bristles move out of contact with the roller they quickly springback to normal relaxed position, thus atomizing and propelling thewetting fluid which they have picked up against the surface of the formroller 24. The fluid which is thus atomized and propelled is in veryfine uniform particles. In fact it is so fine that it is invisible tothe human eye. The form roller 24 is coated with ink, which has a greasebase, and the fine particles of moisture which arepropelled'thereagainst adhere to the outer surface of the ink but do notmix therewith. Since the brush 64 extends the length of the form roller,and since it has uniform and even contact with the fluid conveyingroller 61 throughout its length, the atomized moisture is propelledagainst the form roller in a relatively narrow unbroken horizontalstripe parallel to the form roller and is evenly distributed along thesurface of the form roller. The moisture adhering to the ink on the formroller is deposited from the form roller directly on the printing plate4, throughout the Width of the plate, as the form roller rolls incontact therewith. The particles of moisture deposited and received onthe form roller, in effect, hitch a ride on the form roller to theplate, where they immediately adhere to the already wetted non-imagearea of the plate and are pressed against the plate and distributed onthe non-printing area of the plate. Since the image area of the plate iscovered with ink and is not receptive to moisture, the moisture issqueezed off such area onto the non-image area, and no appreciableamount of moisture collects on the image area.

The knurled or roughened surface 62 on the roller 61 holds the bristles65 until they are distorted to greater extent than would be the case ifthe surface of roller 61 were smooth. Therefore, the bristles arereleased at higher velocity so as to atomize the water and propel itmore rapidly against form roller 24. Although a roller 61 with aroughened surface is preferable it will be understood that the devicewould operate to propel atomized moistur employing a roller 61 with asmooth surface.

, An L-shaped bracket 69 is secured to the side plate 46 at each side ofthe printing press by means of cap screws 70. A compression spring 71 isattached between the bracket 69 and the arm 67 so as'to urge the arm 67downward. This presses the brush 64 against the moisture conveyor roller61 to cause the roller to press the bristles down at the point ofcontact as shown in Fig. I.

An outwardly extending lug 72 is secured to the end plate 46' at eachside of the dampening device frame. An adjustment screw 73 isthreadedlyextended through lug 72 and is held in adjusted position by a lock nut74. The upper end of screw 73 is engageable with the arm 67 to limit itsdownward movement and to adjust and limit pressure of brush 64 againstconveyor roller 61, and to adjust the brush 64 in parallel relationshipwith the roller 61 and form roller 24.

A manually operated crank arm 75 is secured to a shaft '76 which isrotatably mounted at each end to spaced side plates 46. A cam lobe 77 issecured to the shaft 76 in position to contact the arm 67 and raise thesaid arm against spring 71 when the shaft 76 is rotated by movement ofthe hand lever 75, thereby lifting the brush 64 away from roller 61while the press is in nonimpression position, as shown in Fig. II. Thisprevents moisture from being propelled against the inking rollers andplate while the press is running in non-impression position.

The pinion shaft 78 is journaled to the side frame 1 of the printingpress, and a pinion 79 is secured to shaft 78. The gear 79 meshes withthe drive gear 11 for the plate cylinder 2 and is rotated when the platecylinder is rotated. The plate cylinder 2, blanket cylinder 7 and im-'pression cylinder 9 are rotated by conventional power and drive means,forming a part of the press, and are rotated in unison throughtheintermeshing gears 11, 12 and 13.

A sprocket wheel 80 is mounted on the pinion shaft 78, and a drive chain81 is extended about the sprocket wheel 80, and a sprocket wheel 82,mounted on the shaft 66, for the brush 64.

The drive chain 81 is extended about a resiliently mounted idler 83which is of conventional construction, the said idler being pivotallymounted at 84 to the side frame 46 of the dampening device, and isspring urged against the chain 81, so as to maintain tension of thechain 81 when the dampening device carriage is shifted with relation tothe frame 1 of the printing press, as hereinbefore described. Thepivoted, spring urged, idler 83 also permits the chain 81 to belengthened when the brush 64 is pivoted upward out of engagement withthe conveyor roller 61, as hereinbefore described.

A pinion shaft 87 is journaled to the side frame 46 of the dampeningdevice. on the shaft 87, which gear meshes with the gear 79 on the shaft78, to thereby rotate the shaft 87. A sprocket wheel 89 is mounted onthe shaft 87, and a chain 90 is extended about the sprocket wheel 89,and a sprocket wheel 91 mounted on the drive shaft 92 of theconventional variable speed transmission 93. The variable speedtransmission 93 is mounted on the outer side of the side plate 46 of thedampening device frame by means of cleats 98 extending outwardly fromsaid frame, and the base of the transmission is secured to said cleatsby means of suitable bolts 99.

A control wheel 94 is provided for the transmission 93, through whichthe output speed of the transmission may be varied.

The output sprocket 95 of the transmission 93 has a chain 96 extendedthereabout and about a sprocket 97 mounted on the shaft 63 for theconveyor roller 61.

. It will be seen that through the medium of the variable speedtransmission, the speed of rotation of the conveyor roller 61 may beadjusted with relation to the speed of rotation of the plate cylinder 2and the brush 64. The

variance of speed of rotation of the conveyor roller 61 varies theamount of wetting fluid picked up by the roller 61 from the pan 59, andtherefore varies the amount of fluid picked up and atomized by thebristles 65 on the brush 64. It therefore varies the amount of moistureapplied to the form roller 24 and to the plate 4.

By means of adjustment of the speed of rotation of the conveyor roller61, the correct amount of moisture applied to the form roller 24 and theplate 4 can be adjusted with relation to the speed of rotation of theplate cylinder 2 and the amount of moisture required by the plate for aparticular job or speed. After such adjustment is made, it isunnecessary to change the adjustment, because the characteristics of thefluid atomizing and applying means, consisting of the conveyor roller61, brush 64 and the form roller 24, do not change to any appreciableextent over a long period of time. The brush 64 has no contact with theform roller 24 or the plate 4, or any other element from which it couldpick up, and become impregnated with, undesirable materials, such asink, grease or lint. Therefore, it will maintain a constantcharacteristic for a long period of time. Thus it is unnecessary torepeatedly change the brush or the other moisture applying elements inthis device, resulting in great saving of labor and down time of thepress.

A pinion gear 88 is mounted Although it is convenient and advantageousto employ an inking form roller, such as 24, as the intermediate rollerfor transferring the dampening fluid to theplate, it will be understoodthat the intermediate roller need not necessarily be an inking roller.It could be one especially provided forsuch purpose.

It is believed that the operation and function of the plate dampeningdevice herein described is apparent from the foregoing description.

While the printing press is in impression position, as shown in Fig. I,with the inking form rollers in contact with the printing plate 4, theplate cylinder 2, blanket cylinder 7 and impression cylinder 9, arerotated in unison through suitable power and drive means, therebyrotating the shaft 7S, as described. Through the shaft 78 and gear '79the brush 64 is rotated by the chain 81. The moisture conveyor roller 61is rotated through the variable speed transmission 93 and the speed ofrotation thereof is adjustable, as described, the conveyor roller speedbeing proportioned to the speed of rotation of the plate cylinder.

It will be noted that the conveyor roller 61 and the brush 64 arearranged to rotate in suitable directions to cause the brush to propelatomized moisture against the face of the form roller 24. It isdesirable that only suflicient moisture be applied to the form roller 24as is required to moisten the non-image area of the plate 4 to theextent required by the particular job, so that no appreciable amount ofthe moisture will be conveyed to the vibrator roller 20. The correctamount of moisture applied can be easily adjusted in the mannerhereinbefore described, and when once adjusted it need not be changedduring the job for which it is adjusted.

It will be noted that the moisture is applied to the form rollerimmediately before it rotates into contact with the plate 4. Therefore,the moisture is applied directly to the plate, and does not pass betweenintermediate inking rollers.

As shown in Fig. l the peripheral surface of rotatable brush 64 ispositioned in close proximity adjacent the peripheral surface of theapplicator roller 24, andthat the roller 24 has a portion whichintersects and extends beyond the plane tangent to the brush roller 64where it contacts conveying roller 61.

It will be further noted in the form of the device shown in Figure Ithat the applicator roller 24 actually extends into the cusp created bythe curved separating surfaces of the brush roller 64 and the fluidconveyor roller 61, thereby providing an enclosed region through whichthe spray is propelled onto the surface of the roller 24, which regionis virtually closed off by the close adjacency between the surface ofthe brush roller 64 and the roller 24. Thereby the spray emanating fromthe brush 64 is substantially confined within said area and theparticles of spray are effectively prevented from being dispersedbetween the brush roller 64 and the surface of the roller 24, therebypreventing an excessive loss of moisture. Such arrangement andrelationship between the brush and rollers 61 and 24 also assures thatthe applicator roller 24 is positioned directly in the path of theprojected, atomized spray so as to intercept substantially all of thesame.

In this connection it will also be noted that the pan roller 61 and theapplicator roller 24 are actually physically separated from each otherby a space, and that the bristles of the brush 64 actually extend intosaid space between the opposed curved surfaces of the rollers 61 and 24.It will further be noted that the atomized spray generated by the brushbristles is projected across said space directly upon the surface of theroller 24 and not against the surface of the plate. Therefore, theobjectionable results of applying spray directly to the plate, ashereinbefore explained, are eliminated.

Attention is further called to the fact that the space or region betweenthe opposed curved surfaces of the rollers 61 and 24 is non-turbulentand constitutes a rela* tively quiescent body of air thereby assuringthat the spray'willnot be scattered'and dissipated, but substantiallyall of same will be applied directly to the roller 24; It will furtherbe noted that there is a definite geometrical. relationship between therollers 64,. 61 and 24 in that lines connecting the centers of saidrollers would form an acute triangle.

Asthe moisture is applied to the form roller and not directly to theplate, no moisture is deposited in the cylinder gap 5 where it couldaccumulate and cause over- .transfer roller.

wetting of the plate adjacent to the gap.

It willbe understood that other and further forms and embodiments of myinvention may be devised without departing from the spirit andscopeofthe appended claims.

I claim: 1. A plate dampening device for a lithographic offset printingmachine comprising, a dampening fluid container disposed on said machineand adapted to contain a quantity of dampening fluid; a fluid supplyroller rotatably mounted on the machine and disposed in said containerwith one side thereof adapted to be immersed in said fluid; fluidtransfer means arranged to transfer dampening fluid received thereby tothe surface of said plate .by pressure contact application, said fluidtransfer means including a fluid transfer roller rotatably disposed onthe machine in parallel and spaced relationship to the supply roller; acylindrical brush rotatably mounted on the machine having springybristles thereon, with the exposed surface of the supply rollerimpressed into the bristles of the brush; the peripheral surface of'saidbrush extending into the region separating the opposed curved surfacesof thetransfer roller and the supply roller; and means to rotate thebrush, transfer roller and supply roller, whereby as the supply rollerand brush rotate the bristles are released from the roller to atomizeand project the fluid from the surface of the supp-1y roller throughsaid' region directly against the surface of the 2. The combinationcalled for in claim 1 with the addition of means to retract the brush,container and supply roller away from the transfer roller when the pressis shifted to non-impression position.

3. The combination called for in claim 1 with the addition of means tointerrupt the propulsion of fluid by the brush when the press is shiftedto non-impression position.

4. The combination called for in claim 1 with the addition of means tovary the speed of rotation of the supply roller.

.5. The combination called for in claim 1 with the addition of means toresiliently urge the brush into contact with the supply roller; andmeans to limit contact between the brush and supply roller.

6. The combination called for in claim 1 with the addition of means topivot the brush away from contact with the supply roller when the pressis shifted to nonimpression position.

7. A plate dampening device for a lithographic offset printing machinecomprising, roller means rotatably mounted on the machine and includinga roller running in contact with the surface of said plate; an elongatecylindrical brush rotatably mounted on the machine in parallelrelationship to the roller means; an elongate fluid retaining traymounted on the machine and extending parallel to the brush adapted tocontain a quantity of plate dampening fluid; an elongate fluid supplyroller rotatably mounted on the machine extending parallel to the brush,having one side thereof adapted to be immersed in said fluid and theother side thereof in rotative contact with the brush, with theperipheral surface of the supply roller impressed into the bristles ofthe brush; said roller means having a portion positioned closelyadjacent, but spaced from, the brush, and another portion l1 positionedwith relation to the plane'tangent to the brush where the brush contactsthe supply roller so as to intercept and confine atomized dampeningfiuid projected from the surface of the supply roller by the releaseofthe brush bristles; and means to rotate the brush, roller I means and.supply roller, whereby as the supply roller and brush rotate thebristles are released from the roller to atomize and project the fluidfrom the surface of the supply roller directly against the surface ofthe roller means for pressure contacting application. to said plate; .8.The combination called for in claim 7 wherein the roller means comprisesa fluid transfer rollerhaving a portion extending into the cusp formedby the brush and the supply roller. I 9. The combination called for inclaim 7 wherein the roller means comprises a fluid transfer rolleragainst which the atomized fluid is directly projected and wherein linesconnecting the centers of the fluid transfer roller, brush and supplyroller form an acute triangle.

10. A plate dampening device for a lithographic offset printing machinecomprising, roller means rotatably mounted on the machine and running incontact with the surface of said plate; an elongate cylindrical brushhaving a multiplicity of springy bristles thereon and rotatably mountedon the machine in parallel relationship to said roller means; anelongate liquid supply means mounted on the machine and including asurface extending parallel to said brush; means for supplying saidsurface of said supply means continuously with a thin film of dampeningliquid; means for mounting said brush adjacent said supply means with anarrow band of said surface impressed into the bristles of the brush tocause said bristles to be deflected while in contact with said band andto thereafter be released to flick dampening liquid from said band infinely atomized form through the adjacent relatively quiescent body ofair; said roller means having a portion positioned closely adjacent butspaced from said brush and another portion positioned with relation tothe plane tangent to said brush at said narrow band so as to interceptand confine the atomized dampening liquid projected from said supplysurface by the release of said brush bristles.

11. A method of applying lithographicplate dampening-liquid to thesurface of a lithographic plate carried by 'a'rot'ating'cylinder havinga gap therein 'by pressure contact with liquid transferring meansrunning in surface contact with said plate for maintaining ink repellentthe non-printing areas thereof, comprising the steps of, providing andrenewing a thin film of dampening liquid of predetermined thickness on asupporting surface generally parallel to the cylinder, engaging saidsupporting surface in a narrow band of contact with the ends of amultiplicity of springy brush bristles located closely adjacent butspaced from said liquid transferring means to cause deflection of thebristles, maintaining said liquid transferring means closely adjacentbut spaced from said bristles and so related to the plane tangent tosaid bristles at said narrow band as to intercept and confine atomizedliquid flicked by said bristles from said narrow band, moving thebristles and said supporting surface relatively to each other to allowthe bristles to spring back to undeflected positions with resultantflicking of the liquid in finely atomized form from said narrow handthrough the adjacent relatively quiescent body of air toward and ontothe surface of said liquid transferring means, and transferring theliquid received by said transferring means to said lithographic plate byrolling contact under pressure.

References Cited in the file of this patent UNITED STATES PATENTS734,168 Great Britain July 27, 1955

